This invention relates to a producing method of a film with through-holes.
Generally, such film is made of a plastic film. A punching machine is used to form through-holes on the film. The punching machine is arranged to pierce the film with needles. In order to improve the accuracy of dimensions (such as diameters and pitches) of the through-holes, it is necessary to improve an operation accuracy of a punching machine. However, such improvement of the punching machine may increase the producing cost of the film.
Accordingly, there is a strong demand for a producing method of a film with through-holes which achieves a high accuracy of the dimensions of the through-holes, without increasing the producing cost of the film.
Further, it is difficult to produce a film with through-holes which inclination angles (from a direction of a thickness of the film) are relatively large. This is because, when the film is pierced with a needle in an inclined direction, the film tends to be bent.
Accordingly, there is a strong demand for a producing method of a film with through-holes which inclination angles (from a direction of a thickness of the film) are relatively large.
It is therefore an object of the present invention to provide a producing method of a film with through-holes, which achieve a high accuracy of dimensions of the through-holes without increasing the producing cost of the film.
Further, it is another object of the present invention to make it possible to produce a producing method of a film with through-holes which inclination angles (from a direction of a thickness of the film) are relatively large.
According to an aspect of the present invention, there is provided a method including the steps of (1) stretching the film in at least one direction in parallel to a surface of the film, (2) forming through-holes in the film in a state the film is stretched, and (3) terminating the stretching of the film after the through-holes are formed.
After the stretching is terminated, dimensions of the film in the stretching direction decrease. Thus, error of dimensions (such as diameters and pitches) of the through-holes of the film also decrease. As a result, the accuracy of the dimensions of the through-holes is improved, without improving an operation accuracy (of a punching machine or the like) in the through-hole-forming step. Consequently, it is possible to achieve a high accuracy of the dimensions of the through-holes of the film, without increasing the producing cost of the film.
In the through-hole-forming step, it is preferred to form the through-holes by punching. With this, the producing cost is relatively low (compared with a laser machining or the like).
In a particular arrangement, a clamp mechanism is used in the stretching step. The clamp mechanism holds at least two sides of the film to stretch the film. With this, the film can be continuously stretched by means of a simple mechanism. Also, with such a clamp mechanism, biaxial stretching is enabled.
Further, the through-holes are formed on at least one row in the through-hole-forming step. With this, the produced film can be employed in an ink transfer printer described below. In such case, the through-holes are faced with heating elements of a thermal line head.
According to another aspect of the present invention, there is provided a producing method of a film (made of shape memory resin) with through-holes. The producing method includes the steps of (1) heating the film to a temperature above a glass transition temperature of the shape memory resin, (2) stretching the heated film in at least one direction, (3) cooling the stretched film to a temperature below the glass transition temperature, (4) forming through-holes in the film, and (5) heating the film to a temperature above the glass transition temperature.
As the stretched film is cooled before the film recovers its original (non-stretched) shape, the film is solidized in a state the film is stretched. Thus, it is possible to keep the stretched state of the film without continuously applying force to the film.
In a particular arrangement, a pair of heat rollers are used to heat the film and to stretch the film. The film is inserted in a gap between the rollers and pressed therein, so that the film is stretched. Optionally, a fan is used to cool the film in the cooling step. The fan is located in the vicinity of the heat rollers.
According to still another aspect of the present invention, there is provided a producing method of a film with through-holes. The film is made of shape memory resin. The producing method includes the steps of (1) forming through-holes in the film, (2) heating the film to a temperature above a shape-providing temperature of the shape memory resin, and (3) stretching the film in at least one direction in parallel to a surface of the film, in a state the film is heated to a temperature above the shape-providing temperature.
The produced film is thinner than the film in the through-hole-forming step. Further, dimensions of the xe2x80x98producedxe2x80x99 film in the stretching direction are larger than those of the film in the through-hole-forming step. Thus, the inclination angles of the through-holes (from a direction of a thickness of the film) of the produced film are larger than those of the through-holes formed in the through-hole-forming step. Accordingly, it is possible to produce a film with through-holes which inclination angles (from a direction of a thickness of the film) are relatively large.
In a particular arrangement, a pair of rollers are used in the stretching step. The film is inserted in a gap between the rollers and pressed therein. The rollers are heated to a temperature above the shape-providing temperature.
The film produced by the above-described producing method can be used in an ink transfer printer. The ink transfer printer includes (1) a thermal head comprising a plurality of heating elements, the thermal head being faced with the film so that the heating elements are faced with the through-holes of the film, (2) a space formed between the thermal head and the film, which holds ink therein, (3) a platen member which urges a recording media to a surface of the film. When the heating elements selectively heat the ink in the space and the film, ink permeates the through-holes of the film and transferred to the recording media.